Radiation therapy in laparotomy-staged patients with Stage I diffuse aggressive lymphomas is moderately successful. This study was designed to improve upon the efficacy of radiation therapy and to eliminate the need for staging laparotomy. In this study, clinical Stage I and IE patients are treated with four cycles of ProMACE-MOPP chemotherapy (at approximately 75% of the dosages of myelosuppressive drugs originally used in ProMACE and MOPP) followed by involved field radiation to 40 Gy. There are 56 evaluable patients entered on study of whom 54 (96%) achieved a complete remission. There has been one relapse. Three patients died: the two who never achieved a complete response, and one woman who had been in complete response for over four years died during her second coronary artery bypass surgery. The treatment is well tolerated and there have been no serious long-term toxicities with a median follow-up of four years. It would be difficult to improve upon these results or to decrease the toxicities.